Robbie, who turns 39 on Wednesday, also revealed he has lost almost 11kg in the space of five weeks after changing his diet because he says he was resembling former strongman and shot-putter Geoff Capes.

Writing on his blog, he said: "So I went on a diet - knocked out sugar (processed) and dairy. Lost 24 pounds in five weeks.

"I was looking like Geoff Capes after the Christmas run, and seeing as 40 is just around the corner... it's time to go all yoga and lentils, or who knows where it could all end."

Robbie became a father for the first time when his wife Ayda Field gave birth to Theodora in September.

Speaking of the song he has written, he said: "TEDDY GOT HER FIRST SONG. It's called Go Gentle. It might be called something else by the time it comes out.

"I sang it to her yesterday as we walked around the estate. She was in a papoose so she was a captive audience. I think she liked it, then she threw up - tough room."

Robbie, who will tour his Take The Crown album in the summer, said he had also been working on another "big project", and said "very excited about what's to come". The singer has been reported to be be working on a new swing album, to follow his 2001 release Swing When You're Winning.

He also talked about how he had been working with his former songwriting partner Guy Chambers "for the first time in many years". "Funnily enough we're a good team. What a treat - I luvs him," Robbie added. The pair split a decade ago after working together for many years, but have since patched things up.